It's only the second body in the solar system "known to simultaneously satisfy all of the basic requirements for life as we know it", scientists from Texas' Southwest Research Institute said on Thursday (NZ time).

The first you might be aware of - it's Earth.

NASA's Cassini probe made several flybys of Enceladus in its 20-year life. The ice-covered moon is so small it would fit between Hamilton and Wellington, and it's -201degC - much, much colder than even Auckland is right now.

Enceladus lets off plumes of water vapour thousands of kilometres into space, and Cassini flew right through one in 2015.

According to the new paper, published in journal Nature, it detected large and complex organic molecules in the plumes, which they believed formed in a subsurface ocean that could be 10km deep and spread across the entire globe.

"Previously we'd only identified the simplest organic molecules containing a few carbon atoms, but even that was very intriguing. Now we've found organic molecules with masses above 200 atomic mass units. That's over 10 times heavier than methane.

"With complex organic molecules emanating from its liquid water ocean, this moon is the only body besides Earth known to simultaneously satisfy all of the basic requirements for life as we know it."

Enceladus.
Photo credit: Getty

One of those requirements is a good fuel source - which previous analysis of data sent back by Cassini provided.

"Hydrogen provides a source of chemical energy supporting microbes that live in the Earth's oceans near hydrothermal vents," said Dr Hunter Waite, co-author.

"Once you have identified a potential food source for microbes, the next question to ask is 'what is the nature of the complex organics in the ocean?' This paper represents the first step in that understanding - complexity in the organic chemistry beyond our expectations."

The presence of organic molecules isn't a smoking gun in the hunt for extra-terrestrial life, but the finding clearly has scientists itching to get another craft to the famously ringed planet as soon as possible.

"Nowhere else can a potentially habitable extra-terrestrial ocean habitat be so easily probed by a space mission as in the case of Enceladus," study lead author Frank Postberg told space.com.

Cassini left Earth in 1997, arriving at Saturn in 2004. It burned up in Saturn's upper atmosphere in 2017, nine years after its originally scheduled end date.

NASA doesn't currently have a trip to the Saturn system planned, but it is considering a return as part of its New Frontiers mission programme. If given the go-ahead, a launch won't be feasible until 2027 due to the long distances between the Earth and Saturn's orbits.